1. Field of the Invention
The present invention relates to a wet-type electrophotographic printer, and more particularly, to a wet-type electrophotographic printer provided with a photocatalystic filter that uses a plasma for completely decomposing a carrier vapor of a high concentration through oxidation, thus being capable of filtering and deodorizing dirt-containing air.
2. Description of the Related Art
Generally, an electrophotographic printer is categorized according to a developing method into a dry type that uses powder toner, and a wet-type that uses a composition of a carrier liquid, such as norpar or toner. Both the dry type and the wet type are used in a printing process of forming an electrostatic latent image on a photoreceptor medium, such as a photoreceptor drum (body), feeding the toner onto the electrostatic latent image to develop the electrostatic latent image into a visible image, and printing the developed visible image onto a sheet of printing paper by passing the paper between a transfer medium that is rotated while being in contact with the photoreceptor body.
While the dry type electrophotographic printer has some disadvantages, such as harmful toner powders, the wet-type electrophotographic printer generates no harmful toner powders and provides an excellent printing quality. Accordingly, the wet-type electrophotographic printer is in demand.
FIG. 1 is a schematic view showing a structure of a conventional wet-type electrophotographic printer 80. As shown, the wet-type electrophotographic printer 80 includes organic photoreceptors 50a–50d, developing rollers 51a–51d, an intermediate transfer belt 70, a fusing roller 40, and laser scanning units 60a–60d. 
A carrier liquid of the wet-type electrophotographic printer 80 consists of a pigment, a binder resin and a charge detector dispersed therein. For developing an image on a printing medium, such as a sheet of paper, in the wet-type electrophotographic printer 80, firstly, an electrostatic latent image is formed on the organic photoreceptors 50a–50d by laser beams emitted from the laser scanning units 60a–60d. Then, a carrier liquid is attached to the electrostatic latent image of the organic photoreceptors 50a–50d by the developing rollers 51a–51d. After that, the developed image is transferred to the printing medium. When the printing medium with the image thereon passes through the heated fusing roller 40, the carrier liquid evaporates into vapor. Since there is a hydrocarbon mixture in the carrier liquid, the vapor may include one of volatile organic compounds (VOCs), such as benzene, acetylene, gasoline, toluene, ethylene, phenol, methanol, butanol, acetone, methylethyl ketone, or acetic acid. Through a photochemical reaction with nitrogen oxide, the VOCs generate photochemical oxide, causing photochemical smog. The VOCs are poisonous chemical substances that pollute air, incite (induce) cancer, and are a precursor of the photochemical oxide.
Because of a bad smell of a carrier vapor and an environmental pollution, usage of the wet-type electrophotographic printer 80 has been checked despite advantages over the dry-type electrophotographic printer.
Particularly, air purifying machines that use a conventional photocatalyst require a UV lamp for photocatalystic activity and subsequent decomposition of an organic substance. However, the photocatalystic activity by the UV lamp, due to a considerably slow response and activation, was not enough to decompose the organic substance, such as the one in the wet-type electrophotographic printer, which accumulates to a high concentration from the beginning of printing.